Dreyfus



April 22, 1958 1.. DREYFUS POLYPHASE STIRRING WINDING Original FiledAug. 10, 1954 HHHIIIIHHIW @UIHHHHHILHHH r u n il l. r mg m 6? i V 4 m wd Y. B

United States Patent POLYPHASE STIRRIN G WINDING Ludwig Dreyfus,Vasteras, Sweden, assignor to Allrnanna Svenska Elektriska Aktiebolaget,Vasteras, Sweden, 8 Swedish corporation Original No. 2,759,035, datedAugust 14, 1956, Serial No. 448,841, August 10, 1954. Application forreissue April 25, 1957, Serial No. 658,904

Claims priority, application Great Britain August 11, 1953 17 Claims.(Cl. 13-26) Matter enclosed in heavy brackets I: appears in the originalpatent but forms no part of this reissue specification; matter printedin italics indicates the additions made by reissue.

The present invention relates to an improvement in stirring windings formelting furnaces or hot metal mixers.

In hitherto. known stationary stirring windings for arc furnaces thewinding is fed by symmetrical two-phase current with the result that thephase position of the A. C. currents changes from one current zone tothe following zone with 90 displacement. Since there are five currentzones, 1, 2, 3, 4, (having respectively n n n n, and n conductors), thephase position for the two outermost zones 1 and 5 is the same. Due tothe fact that the winding is mounted symmetrically with respect to themiddle with the numbers of conductors in the five zones having therelationship,

and n =n the two phases 1, 3, 5 and 2, 4, respectively, do not induceeach other. These known stirring windings have been constructed asconventional coil windings, i. e. like the stator windings of polyphasesynchronous generators or asyn-chronous motors. Thus the winding isembedded in a coarsely laminated slotted iron core and is fixed thereinby laying the conductors into the slots and by staying the longdouble-curved ends of the coils by means of strong screw joints.

The above described stirring windings have the disadvantages that theirmanufacture is expensive, that a large stock of spare parts is required,since the coils are of unequal dimensions, and the winding requires alot of space.

The stirring winding according to the present invention, by means ofwhich the above drawbacks are all overcome, is characterised in that theWinding consists of hollow coils, which slide on to coarsely laminatedyokes without slots for retaining the conductors, and in that thewinding of each yoke consists of five successive sections 1, 2, 3, 4, 5having numbers of turns n =n n =n n, 5 2n; and is fed symmetrically fromtwo phases so that the current in one phase has 90 phase displacementwith respect to the current in the other phase.

Such a stirring winding consists of five coils which can be wound in asimple winding machine. The coarsely laminated yoke may consist of twostraight legs, which are joined together and positioned below the bottomof the furnace.

Two embodiments of the invention will now be described by way of examplewith reference to the accompanying drawing, in which Figure 1 shows oneform of the stirring winding arranged below the bottom of the furnace,

Figure 1a is a wiring diagram for the coils of the stirring winding, I

Figures 2 and 2a show modified forms of a part-of the winding Figure 1,t

Re. 24,462 Reissued Apr. 22, 1958 Figure 3 is an end view of the windingand core parts shown at Figures 2 and 4,

Figure 4 is a view corresponding to Figure 3 but showing a modified formof windings and cores arranged below a furnace bottom having stayinggirders.

Referring to Figures 1-3, thebottom of the furnace is designated by 10.The stirring winding, generally designated by 20, is a two-phase windingfor a furnace having a curved bottom. The coarsely laminated iron yokehas its laminations indicated by vertical lines in Figures 3 and 4 andconsists of two straight legs 30, which are joined together at an angleof 180u, where the centre angle of the furnace bottom is 21:. Each legsupports coils having three current zones 1, 2, 3' and 3", 4, 5respectively, wherein 3' and 3" constitute one current zone. Thecondition for symmetry is that the number of turns of the current zonesn ==n n =n but for the total number of turns of the middle zone n (n,+nis permissible. The wiring diagram for the coils of the stirring windingis shown in Figure 1a. The coils 1, 3', 3" and 5 are fed from one phasewhile the coils 2 and 4 are fed from the other phase, the directions ofthe currents being indicated by full line arrows and dotted line arrows,respectively, for the corresponding phases. The lightest yoke isobtained with n (n +n The coils of this configuration are all of equalradial dimensions so that the keeping of a stock of spare parts isfacilitated. The coils are insulated from each other by means ofintermediate pieces 80. The stirring windings may be protected by meansof members of refractory material positioned between the winding and thebottom of the furnace. Ventilation and cooling ducts 40 are arrangedbetween the yoke 30 and the coils 20. See Figures 2 and 4, the flow ofair being indicated by the arrows in Figure 2. Spacer bars are insertedbetween the coils and the yoke. The winding may also be constructed forinternal water cooling as indicated in Figure 2a.

Measures may be taken for minimising the reactive power of the winding.In contradistinction to the coil winding of the conventional type, inthe new winding approximately the same fiux per cm. length of conductoremerges from its lower side and short sides. This flux does notcontribute to the stirring forces but increases the reactive power tothe same amount as or somewhat above the amount occurring in coilwindings of the known type. It is therefore suitable to make the casing50, by means of which the winding has to beprotected, of metal of lowelectric ohmic resistivity. In this case, eddy currents are generated inthe casing, which eddy currents minimise the ineffective part of themagnetic flux with the result that the reactive power is reduced.

In the case of a furnace with a plane bottom the yoke may consist of twostraight legs, such as the legs 30 of Figure l, which legs are joinedtogether in alignment with each other and suitably reinforced. The.middle current zone would be divided into two equal halves.

Finally the invention permits the division of the stirring means alongtheir width into two or more narrower stirring means of equal length andequal zone distribution, which further facilitates the keeping of astock of spare parts. This construction also permits the introduction ofone or more girders (preferably of non-magnetic material) which act asstaying means for supporting the bottom of the furnace. This embodimentis shown in Figure 4. The staying means are indicated by the numeral 60.

Although the new windings are described for use with melting furnaces,it lies in the scope of the invention to use them for hot metal mixers.

I claim as my invention:

1. Polyphase stirring winding system for stirring the metallic charge ina container for molten metal, comprising hollow coils, at least onelaminated non-slotted magnetic yoke arranged below the bottom of thecontainer and within said coils, the winding system of the coilsconsisting of five successive sections 1, 2, 3, 4, 5, having numbers ofturns n =n n =n 11 211 and being'supplied with a polyphase current forsymmetrically feeding the said successive sections so that the currentin the one phase has 90 phase displacement with respect to the currentin the other phase.

2. A polyphase stirring winding system according to claim 1, in whichthe middle section of the winding is divided into two equal halvessymmetrically disposed about a central plane at right angles to thelongitudinal extension of the winding.

3. A polyphase stirring winding system of the type described, comprisingfive'successive sections arranged endto-end and with the middle sectiondivided into two equal halves disposed symmetrically about a centralplane at right angles to the longitudinal extension of the Winding, anda yoke consists of two equal legs joined together in alignment with eachother to provide a reinforced junction.

4. A polyphase stirring winding system of the type described, comprisingfive successive sections placed below a curved bottom of a molten metalcontainer having a center angle of 2a, and the middle section beingdivided into two equal halves disposed symmetrically about a centralplane at right angles to the longitudinal extension of the winding, anda yoke consists of two equal legs forming 'an angle of approximately180-a at their junction point to provide a reinforced junction.

5. A polyphase stirring winding system according to claim 1, comprisingintermediate pieces whereby the coils carrying current of differentphases are insulated from each other and a space provided between thecoils and the yoke'for the purpose of cooling.

6. A polyphase stirring winding system according to claim 1, comprisingmetallic members of low ohmic resistivity covering at least apart of thelateral and lower sides of the coils for minimizing the ineffective partof the magnetic flux.

7. A polyphase stirring Winding system according to claim 1, in which atleast two such stirring windings in substantially parallel relationshipwith each other are arranged below the container, and comprisingsupporting means arranged between said windings for staying the bottomof the container.

8. In combination with a container of molten metals 4 and having abottom, on induction stirrer for such metal having a winding systemcomprising a plurality of stationary electrical coils positionedadjacent the bottom of said container, said coils having an axis of thewinding l'h'er'eof generally parallel to said bottom, the winding systembeing symmetrical with respect to a plane through the bottom of saidcontainer at right angles to a line joining the central points of thetwo ends of the winding system, and a poly-phase power source forcnergising said coils and producing ampere-turns therein, theampore-turns of one part of the system being 90 out of phase withrespect to the ampere-turns of another part of the system.

9. A device as claimed in claim 8, said winding sysfem including onepart comprising two coil sections, said sections being connected to onephase of said power source and spaced apart from each other and havingtheir ampere-turns 180 out of phase with each other, and another partconnected to another phase and located between said spaced coilsections.

winding system being divided into two equal halves symmetricallydisposed about said plane.

12. A device as claimed in claim 8, said winding system consisting offive successive coil sections, 1, 2, 3, 4, 5, having numbers of turns n=n n =n u 5211 the sections 1, 2 and half of section 3 being arrangedsymmetrically in respect to the sections 4, 5 and the other half ofsection 3 about said plane, the sections 1, 3, 5, being connected to onephase, the sections 2, 4 being connected to another phase of saidpoly-phase power source.

13. A device as claimed in claim 8, said winding-system comprising fivesuccessive coil sections arranged endto-end and with the middle sectiondivided into two equal halves disposed symmetrically about said planeand a yoke comprising two legs, said legs joined together in alignmentwith each other.

14. A device as claimed in claim 8, said winding system comprising fivesuccessive coil sections placed below a curved bottom of a molten metalcontainer, said bottom having a centre angle of 2a, and the middlesection being divided into two equal halves disposed symmetrically aboutsaid plane, and a yoke comprising two legs, said legs joined togetherand forming an angle of approximately 18 0oc.

15. A'device as claimed in claim 8, the winding system comprisingintermediate pieces whereby the coils carrying current of difierentphases are insulated from each other and a space provided between thecoils and the yoke for the purpose of cooling.

16. A device as claimed in claim 8, the winding system comprisingmetallic members of low ohmic resistivity covering at least a part ofthe lateral and lower sides of the coils for minimizing the inefiectivepart of the magnetic flux.

17. A device as claimed in claim 8, said induction stirrer comprising atleast two winding systems in substantially parallel relationship witheach other below the container and comprising supporting means arrangedbetween said systems for staying the bottom of the container.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS 1,013,359 Appel Jan. 2, 1912 1,076,887 Howard Oct.28, 1913 1,791,934 Northrup Feb. 10, 193 1 1,851,984 'Rennerfelt Apr. 5,1932 1,937,065 Moore Nov. 28, .1933 1,943,802 Northrup Ian. 16, 19342,513,082 Dreyfus June 27, 1950 2,620,366 Ladell Dec. 2, 1952 2,652,441Gynt etal Sept. 15, 1953 2,686,823 Jones Aug. 17, 1954 2,759,035 DreyfusAug. 14, 1956 2,767,236 Williamson Oct. 16, 1956 FOREIGN PATENTS 499,437Great Britain Jan. 24, 1939

